Instant portable bar code reader

ABSTRACT

An improved bar code reader unit. The bar code is hand-held and has improved focussing and illumination structure.

This is a continuation of application Ser. No. 334,811, filed Dec. 28,1981, now abandoned.

BACKGROUND OF THE INVENTION

The present application is particularly directed to improvements in theinvention of our U.S. Pat. No. 4,282,425 issued Aug. 4, 1981. Thedisclosure of said patent is incorporated herein by reference,particularly for purposes of background information.

SUMMARY OF THE INVENTION

The present invention, in one important aspect, is directed to theprovision of a particularly facile and effective hand held reader unitfor the instantaneous reading of complete bar code patterns of curved orirregular configuration, and comprising an optical system whichaccomodates itself to a compact and rugged, yet lightweight constructioncapable of economical manufacture.

In another aspect, the invention provides a high speed bar code readersystem and method which is capable of reading a complete bar codepattern as an entity for computer processing without requiring thereader unit to be moved during the read-in operation; such system andmethod being further optimized by the provision of a flash illuminatorof special configuration for providing a particularly uniform obliquelydirected light output over the full depth of the optical field of thereader lens system, and by the provision of a lens system which isadjusted in its spectral response and stop aperture characteristics soas to achieve a high resolution and accuracy over a sufficient depth offield to read high density bar patterns with marked curvature or surfaceirregularity.

It is therefore an important object of the invention to provide aportable instant bar code reader and method providing improved opticalcharacteristics.

Another object resides in the provision of a bar code reader system andmethod exhibiting an improved flash type illuminator.

It is also an object of the invention to provide a portable instant barcode reader system and method wherein the optical and electronicconstruction are interrelated so as to provide for quick-repeat, moreaccurately focussed reading where an initial reading is ineffectivebecause of marginal reading conditions or the like.

Still another object resides in the provision of a hand held bar codescanner having novel electronic, optical and structural features adaptedto the implementation of the various objects set forth above.

Features of the invention include the provision of a reader unit with awide field of view and substantial focal depth, which yet has a narrowhand grip configuration, and a compact optical system; an optics systemwhich accomodates a single unitary circuit board configuration, a rigidlens mounting arrangement which furthers the achievement of a preciseand reliable optical system with a dust and moisture proof enclosure andsubstantial impact resistance; and an optical system providing anoptical field of extended depth coupled with an optimum focus at aselected close up position and electronics for signalling an inaccuratereading and automatically repeating the read operation if necessary asthe operator adjusts the unit toward the optimum reading position untila valid reading is achieved.

These and other features, objects and advantages of the presentinvention will be understood in greater detail from the drawings and thefollowing description wherein reference numerals illustrate a preferredembodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a somewhat diagrammatic perspective view illustrating ahand-held reader unit and associated components in operative readingassociation with a bar code pattern on a container;

FIG. 2 is a somewhat diagrammatic longitudinal sectional view showingthe general layout and configuration of the reader unit of FIG. 1;

FIG. 3 is a somewhat diagrammatic plan view of the reader unit of FIG. 2with a top casing part removed and internal components diagrammaticallyindicated;

FIG. 4 is an enlarged partial somewhat diagrammatic view of the readerunit of FIG. 3, the section of FIG. 4 being taken along the lines IV--IVof FIG. 3;

FIG. 5 is a somewhat diagrammatic, cross-sectional view taken along theline V--V of FIG. 4;

FIG. 6 is a somewhat diagrammatic, cross-sectional view taken along theline VI--VI in FIG. 4;

FIG. 7 is a diagrammatic illustration showing exemplary details of asuitable electric circuit configuration for the system of FIGS. 1through 6;

FIG. 8 is a somewhat diagrammatic view illustrating the basic optics ofthe illustrated embodiment and showing the lens arrangement generally inthe plane of FIG. 3;

FIG. 9 is a plot illustrating lateral aberrations for the system ofFIGS. 1 through 8;

FIGS. 10 and 11 show optical transfer functions for the system of FIGS.1 through 9, FIG. 10 being for the "Through Focus" condition and FIG. 11being for the "Best Focus" condition;

FIGS. 12, 13 and 14 illustrate radial distortion, geometricalastigmatism, and MTF astigmatism, respectively, for the system of FIGS.1 through 11; and

FIGS. 15 and 16 together provide a diagrammatic showing of the electriccircuitry for the interface component 17, FIG. 1, where the unit 16 isitself battery operated and portable.

DETAILED DESCRIPTION

Referring to FIG. 1 there is illustrated an overall bar code readersystem in accordance with the present invention, and showing a hand-heldreader unit 10 in scanning relation to a bar code pattern 11 associatedwith a product container 12. By way of example, the bar pattern 11 maybe formed in accordance with the universal product code and may have alength of 65 millimeters. Various other bar code types are known in theart, such as EAN, CODBAR, CODE 39, INTERLEAVED 2/5, etc.

The hand-held unit is shown as comprising a case 14 including a portion14a of a size to be gripped by the user, a head portion 14b forcontaining the reading optics and a connecting portion 14c integrallyconnecting the hand-grip portion 14a with the optical reading headportion 14b. The head portion 14b has a width so as to be operative toreceive a sufficient portion of the bar pattern 11 so as to completelyread the same while the head portion 14b is in essentially stationaryrelationship to the bar pattern 11. Thus, the head portion 14b may havean overall width of 3.0 inches and may have an overall height dimensionof one inch. On the other hand, the hand grip portion 14a may taper froman overall width of about one and one-half inches adjacent theintermediate portion 14c to a width of about 0.828 inch at its rear end.The height dimension of the hand grip portion 14a may likewise taperslightly from the intermediate portion toward the rear end portion, froma height dimension of about one and one-quarter inches to aboutthree-quarter inches. The lower margins such as 14d of the hand gripportion 14a are smoothly rounded for example with a radius of curvatureof 0.46 inch, the bottom wall of the hand grip portion 14a being formedon a radius of 5.00 inch in the transverse direction so as to enhancethe comfort with which the hand grip portion can be grasped. The forwardportion of the hand grip portion 14a has a perimeter such that the thumband first finger of the hand are normally overlapping or touching duringhandling of the reader unit 10.

With the reader unit 10 resting on a horizontal surface, theintermediate portion 14c will have a separation of approximatelythree-eighth inch above the horizontal surface, while the top surface14e of the head portion 14b will extend at a pronounced acute angle tothe horizontal which facilitates observation of the bar code pattern asthe unit 10 is placed in scanning relation thereto by the user. Forexample, with the unit 10 resting on a horizontal surface, the uppersurface 14e of the head portion 14b may be inclined at an angle of 25°to the horizontal.

The length of the hand grip portion 14a may be about four inches so asto be comparable to the width of the hand when placed in comfortablegripping relation to the unit 10. The overall length of the head portion14b with the unit 10 resting on a horizontal surface may be about twoand one quarter inches measured in a horizontal direction.

A cable 15 is indicated as connecting the unit 10 with host equipment 16via a suitable link or interface 17. For the case of portable equipment,unit 16 may include a battery, and link 17 may include a batteryoperated high voltage power supply as well as suitable signal interfacecircuitry. In this way the complete system of FIG. 1 may be completelyportable, without requiring any connecting wires to stationaryequipment.

The reader unit 10 may have a weight of eight ounces, an overall lengthof 7.38 inches, an overall width of 2.63 inches, and a thicknessgenerally of one inch except at a raised section 14f at the rear end ofthe head portion 14b.

An important feature of the unit 10 of FIG. 1 relates to the provisionof a hand-held reader configuration whereby the unit can be readilymanipulated in all degrees of freedom and be held at a desired angularrelationship to a product container or the like with the four fingersand palm of the hand while the thumb of the user is utilized to depressan operating button 18 located centrally of the top surface of the unitand at the forward end of the hand grip portion 14a. While with theillustrated embodiment a complete reading of the bar pattern 11 takesplace in an extremely brief instant, a stable gripping of the hand-heldunit during operation is still desirable for the sake of comfort and tominimize fatigue over an extended period of use.

While the bar code pattern 11 is shown on a flat planar surface, it issignificant that the reader unit 10 is also effective with curved orirregularly shaped labels. Thus, the bar code pattern 11 may be readeven though it extends along a curved surface having a radius ofcurvature of 1.25 inches, for example. Such a label with a 1.25 inchradius of curvature and with a length dimension of 1.8 inches requiresreading of a field with a depth of about 0.4 inch, for example. Thus,certain portions of the bar code pattern 11 may be in direct contactwith the operative end of the unit 10 while other portions of the barcode pattern may be spaced by distances of up to 0.4 inch. Theillustrated unit is thus effective in reading bar code patterns appliedabout the curved perimeter of cylindrical containers such as cans, aswell as bar code patterns applied to flexible bag type containers andthe like.

DESCRIPTION OF FIGS. 2 AND 3

FIG. 2 is a longitudinal sectional view of the hand-held reader unit 10of FIG. 1 illustrating the arrangement of parts therein; and FIG. 3 is aplan view of the reader unit 10 with an upper section of the case 14removed to show the layout of parts internally of the unit. These viewsshow a printed circuit board 20 having a rear section 20a with amicrocomputer integrated circuit pack 21, a bidirectional line driverintegrated circuit pack 22, and an analog switch integrated circuit pack23, for example. Referring to FIG. 2, an intermediate portion 20b of thecircuit board 20 carries centrally thereof a photodetector integratedcircuit pack 24. As seen in FIG. 3, the intermediate portion 20b of thecircuit board carries other components such as an operational amplifierpack 25, a "beeper" component 26 and a transformer 27. In FIG. 2 at aforward portion of the casing 14, a flash energy storage capacitorassembly is physically designated by reference numeral 30, and atriggering capacitor is indicated physically by reference numeral 31. Asseen in FIG. 3, the forward portion of the circuit board 20 is separatedinto two finger portions 20c and 20d arranged at the lateral margins ofthe case portion 14b.

At the extreme forward end of the casing 14 is an optical window 34which serves for the optical coupling of the unit 10 with a bar codepattern such as indicated at 11 in FIG. 1. Adjacent a lower portion ofwindow 34 is a flash reflector 35 forming a part of a reading lightsource assembly 36, shown in further detail in FIG. 4. The light source36 serves to project a sheet of light through the window 34 for floodinga sensing region of substantial depth in front of the window 34, inwhich region the bar code pattern 11, FIG. 1, is to be located. Thelight reflected by a bar code pattern in the sensing region is reflectedback through the window 34 so as to impinge on a first mirror 41 of amirror assembly 42. Light incident upon the mirror 41 is reflectedforwardly toward a second mirror 43 of a second mirror assembly 44. Fromthe second mirror 43, light from the sensing region is directedrearwardly into an optical housing 46. The optical housing 46 togetherwith the mirror mounts 42 and 44 are parts of a unitary opticalframework which rigidly mounts all of the optical parts includingmirrors 41 and 43 and the other optical components including an infraredrejecting filter 47. Further details of the optical system will beapparent from the following description of FIGS. 4-6.

Referring to FIGS. 2 and 3, the width dimension of the reflector 35 oflight source 36 may be approximately 2.29 inches, so as to effectivelyilluminate a sensing region in front of the optical window 34 which mayhave an extent of about 2.5 inches directly in front of the opticalwindow 34 and an extent of about 2.7 inches at a depth of one inch infront of the window 34. Thus, the total width of the image field may betaken as approximately 65 millimeters at a distance of approximatelyfour millimeters from the center line of the optical window 34. Thus, asviewed in FIG. 3, the marginal rays of the light image entering the unit10 through the window 34 from the sensing region and converging on thefirst mirror 41 may each form an angle of convergence relative to acentral longitudinal axis of the optical system having a value in therange from about ten degrees to about twenty degrees. Thus, as viewed inFIG. 3, a sensing region 50 in front of the optical window 34 may bedefined by marginal light. rays such as indicated at 51 and 52 which aredirected through the optical window 34 and converge toward therespective lateral margins of the first mirror 41. The width of thesensing region 50 may be at least fifty millimeters, and the depth ofthe sensing region 50 may be at least about three millimeters, andpreferably at least about ten millimeters. The optical system should beeffective to focus the bar code pattern 11, FIG. 1, onto thephotodetector 24 for positions within the sensing field 50 with aresolution of at least about forty line pairs per millimeter for anangle of convergence of each marginal ray 51, 52 of about fifteendegrees relative to the central longitudinal axis of the optics asviewed in FIG. 3. This corresponds to resolving bars having a widthdimension in the direction of high resolution of about 125 microns (fivemils, one mil equals 0.001 inch).

The first mirror 41 may have a length dimension of about 1.6 inches,while the second mirror 43 may have a length dimension of about 1.2inches, for example. The lateral margins of the first mirror 41 areindicated at 41a and 41b in FIG. 3, while the lateral margins of themirror 43 are indicated at 43a and 43b in FIG. 3. The marginal lightrays as reflected from the mirror 43 toward the filter 47 are indicatedat 53 and 54 in FIG. 3. The further margins of the light energy from thesensing region as it passes through the lenses of the optical system areindicated by the dash lines 55 and 56 in FIG. 3. As will be describedparticularly with reference to FIG. 6 hereafter, the light energytransmitted by the optical system is converged so as to pass through anaperture with a width in the high resolution direction of the bar codepattern 11 with a dimension of about two millimeters, for example. Forthe illustrated embodiment, the light energy from the sensing region 50after passing through the narrow optical aperture within the housing 46,diverges over a substantial distance and comes to a focus at a lightsnesing region of the photodetector 24 having a dimension in the highresolution direction of 26 millimeters, for example, the image from thebar code region 50 being focused in inverted relation onto the lightsensitive region of the photodetector 24.

The infrared filter 47 may serve to essentially block infrared radiationhaving a wave length greater than about 700 nanometers. It is consideredthat better contrast is obtained by filtering the infrared portion ofthe light spectrum entering the window 34 from the sensing region 50.Further, it is considered that improved resolution is obtained over thedesired depth of the sensing region 50 because of the presence of theinfrared filter 47.

The optical window 34 may have a thickness of about 2.5 millimeters andbe of a tempered glass material so as to be readily cleaned whileresisting breakage. The image of the bar code pattern may be focusedonto the light sensitive region of the photodetector 24 through a quartzwindow having a thickness of 0.5 millimeter and across an air gap of1.14 millimeter, for example. Thus, the ratio of the length of the imageat the bar code sensing region 50 to the length of the focussed image atthe light sensitive region of the photodetector 24 may be about 2.5, forexample.

DESCRIPTION OF FIGS. 4, 5 AND 6

FIG. 4 is a partial enlarged longitudinal sectional view of the readerunit 10, taken along the lines IV--IV of FIG. 3.

From FIG. 4 it will be seen that light source 36 includes a flash tube60 which extends for the length of the light source assembly 36. Forexample, flash tube 60 may have an overall length of 68 millimeters, andmay have right angle end portions such as indicated at 60a extendingrearwardly from the assembly 36 through slots such as indicated at 61.The tube 60 may have a diameter of four millimeters and may have itscenter located at a focus of an eliptical portion 35a of reflector 35.Thus, a light ray such as indicated at 62 emitted from the center of thetube 60 will be reflected at the eliptical portion 35a and impinge inthe bar code sensing region 50 at a point 63 representing a second focalpoint with respect to the elliptical configuration of reflector portion35a. Point 63 is illustrated as lying on an optical axis 64 whichintersects the first mirror 41 at a central point. Line 66 in FIG. 4 mayrepresent a surface of a container such as 12 containing a bar codepattern such as indicated at 11 in FIG. 1. Marginal rays of lightreflected from the surface 66 in the plane of FIG. 4 are indicated at 67and 68, for example.

The eliptical portion 35a has an axis such as indicated at 70 which isinclined relative to a normal to the surface of window 34 by an acuteangle such as 21°. Thus, light reflected from the eliptical portion 35ais generally directed upwardly and obliquely to the central optical axis64.

Light directed away from the eliptical portion 35a from the center oftube 60 impinges on a segmental cylindrical portion 35b which serves toredirect the light onto the eliptical portion 35a, again for furtherreflection in a generally upward direction and obliquely to the centralaxis 64.

The direct light from tube 60 which penetrates the sensing region 50 isalso directed generally upwardly and obliquely to the central opticalaxis 64.

The resultant direct and reflected light from tube 60 floods the sensingregion 50 and defines a sheet of light directed into region 50 obliquelyto the central optical axis 64.

As illustrated by dot dash line 80, mirror 41 reflects incoming lightenergy along an axis 80 from its front surface, and mirror 43 reflectslight impinging thereon along a central axis 81 from its front surface.

The light energy directed along the axis 81 impinges on the infraredfilter 47 in a substantially normal or perpendicular direction, and thetransmitted light energy then traverses a lens system including lenses91-95. Between lenses 92 and 93 there is provided a light stop member 97providing a rectangular optical aperture 98. The aperture 98 has a widthdimension extending in the high resolution direction of the opticalimage being transmitted which is substantially less than the verticaldimension corresponding to the direction of low resolution (parallel tothe bars of the bar code pattern 11). By way of example, the horizontaldimension of the aperture 98 may be about two millimeters while thevertical dimension may be about four millimeters.

The lenses 91-94 are rigidly mounted by means of a lens barrel 100having a key 100a fitting into a slot 101 of the optical housing 46. Thelight stop member 96 may be integral with this light barrel 100. Each ofthe lenses 91-94 may be symmetrical with respect to the centrallongitudinal axis 81 passing through the center of the rectangularaperture 98.

As seen at the right in FIG. 4, the optical axis 81 intersects areflecting mirror 103 whose front surface is reflective so as to directthe light energy along an axis 104 normal or perpendicular to the lightsensitive surface of the photodetector 24 which is mounted on theprinted circuit board 20 at the intermediate region 20b.

DESCRIPTION OF FIG. 7

FIG. 7 is an overall diagrammatic view showing the electric circuitrywhich is housed within the portable hand-held unit itself. The followingdescription applies to the operation of this circuitry whether it isassociated with a portable battery operated terminal or with a fixedinstallation such as a cash register, computer port or the like.

The hand-held unit is placed near the bar code pattern to be read andthe trigger switch actuator associated with switch S1, FIG. 7 ismomentarily depressed. In response to such signal from switch S1 or acomparable proximity sensor, microprocessor A1 outputs a signal to theflash tube section indicated at 7-1 in the lower right portion of FIG.7. The tube MFT flashes and the bar code image is reflected through anoptical system to a 1024 element diode array line scanner indicated atA3 in the upper left of FIG. 7. This image is rapidly shifted out,filtered, amplified and squared up before passing to the "Data In" input7-2 of the microprocessor A1.

The microprocessor A1 processes this input data, calculates bar spacingand widths and derives the bar code number. If the number is not valid,the microprocessor retriggers the flash tube MFT and repeats the readingprocess. The final valid number is serially shifted out of themicroprocessor A1 and into the data device such as a Norand model 101terminal, a cash register, a computer port or the like.

In point of sale (POS) applications, the microprocessor A1 is left oncontinuously. When first turned on, input 7-4 of microprocessor A1(RESET) is held low by capacitor C1. The capacitor C1 charges and wheninput line 7-4 exceeds 2.5 volts, the microprocessor is ready to beginprogram execution.

In a portable application utilizing battery power, the reader unitoperates from a battery pack, and to prolong its life, themicroprocessor is powered down when not needed. With such portableoperation, when trigger switch S1 is closed, a scan proximity line 7-5goes low, this line being connected with a model 101 terminal. Suchterminal then applies 5 volts at input line 7-6 so as to supply power tothe microprocessor A1. With power applied, capacitor C1 charges and whenits voltage value is above 2.5 volts, the microprocessor is placed inoperational condition. In addition, output line 7-7 from microprocessorA1 is isolated from the flash tube circuit 7-1 by means of a bilateralswitch A54. During power up and down, the potential on output line 7-7changes unpredictably and could flash the lamp MFT; to prevent this,bilateral switch A54 is opened during this interval.

The microprocessor A1 controls all functions within the hand-held unit.For the illustrated embodiment, the application program may reside in anexternal programmable read only memory PROM. To access the PROM, themicroprocessor outputs the address as two data groups. The low addressbits are placed onto the data bus 7-12 through 7-19 and are latched by adata latch associated with the PROM circuit when output 7-11 goes highthen low again. The microprocessor then outputs the remaining address onoutput lines 7-21 through 7-24. The PROM retrieves the data byte fromthe location chosen by the address bus. When output line 7-9 from themicroprocessor goes low, the PROM outputs are enabled and output thedata byte onto the data bus for transfer to microprocessor A1. Inanother embodiment of the invention, the microprocessor A1 will includeup to four kilobytes (4K) of internal factory masked program read onlymemory.

The flash tube section 7-1 is powered via lines 7-25 and 7-26 from anexternal power source. A voltage of 310 volts is supplied from a usersupplied source of power. A voltage of 400 volts may be supplied fromthe model 101 previously mentioned. The applied power charges a chargestorage capacitor C6 connected across the miniature flash tube MFT. Theflash tube contains two electrodes with Xenon gas separating them. Afine wire is wound around the cathode end of the tube. When a highvoltage is applied to this wire, the Xenon gas is ionized, lowering theresistance between the end electrodes. The gas breaks down, releasinglight energy in the process. The capacitor is rapidly discharged as avery high current spike creating the intense light output. When thecurrent and voltage fall below the gas sustaining potential, the flashis extinguished and the gas again becomes nonconductive. The actualflash is of very short duration.

To create the trigger voltage, the 310 volts is stepped up by a triggertransformer L1 and capacitor C7. In the quiescent state, a siliconcontrolled rectifier SCR1 is non-conducting and the trigger circuit isopen. The capacitor C7 in series with the primary of transformer L1 ischarged to 310 volts peak through a current limiting resistor R17.

When the microprocessor is ready for a flash it drives output line 7-7high so as to cause the silicon controlled rectifier SCR1 to conduct andto complete the trigger circuit. Current flows from the capacitor C6through SCR1 to the other side of the trigger transformer L1. The 310volt capacitor pulse is stepped up through transformer action to over4,000 volts (4 KV) and is sent to the flash tube MFT, triggering aflash. The capacitor C6 is discharged, and the loop current decaystoward zero. Output line 7-7 returns to a low potential condition andwhen the current through SCR1 is less than its latch-up value, SCR1returns to the non-conducting state and the capacitor C6 beginsrecharging.

For point of sale applications, capacitor C6 is a low leakageelectrolytic and is constantly across the power supply. This allowsrapid recharge and flash rates to occur.

For the case of a portable power supply, power for capacitor C6 isgenerated by a small step-up converter that is located in the portableinterface module. There is also a sense circuit that monitors thevoltage on the charged storage capacitor C6 and turns off the converterwhen the capacitor is charged, and turns it back on again after a flashor when the capacitor charge has leaked down to approximately 375 volts(375 VDC). Because this unit is operating off of battery power, it takesmuch longer to recharge the capacitor than in the case of a point ofsale unit. Recharge time takes from 300 to 500 milliseconds (300 to 500MSEC), depending on the state of the batteries.

Component A3 in FIG. 7 is a 1024 element line scanner, for example,Reticon RL 1024 G integrated circuit pack. The scanner component A3comprises a row of silicon photodiodes, each with an associated storagecapacitor on which to integrate photocurrent, and a multiplex switch forperiodic readout via an integrated shift register scanning circuit. Eachphoto diode capacitor is charged to a known level; then the array isexposed to the bar code. Light areas cause the photodiodes to dischargetheir associated capacitors while dark area photodiode capacitors retainfull charges. The shift register scanner is stepped from element toelement and the capacitor voltage level is read out to themicroprocessor until all 1024 elements have been read.

Within the scanner are two photodiode arrays. Both arrays containphotodiodes and capacitors. The video array produces the actual bar codeimage while the dummy array is masked from the light source. Scannerswitching noises are induced capacitively into both arrays and interferewith the video signal. As the scanner is stepped, the video and dummyoutputs are presented to an external differential operational amplifierA6. The common mode noise on the lines is effectively cancelled, leavingonly the video differential signal for further processing.

The microprocessor A1 controls all signals that cause the scanner A3 tooperate. Before the flash tube is fired, the scanner capacitors arecharged to +5 volts (+5 V). Microprocessor output 7-28 goes high thenlow at the START input of scanner A3 to reset the scanner internal shiftregister to the first element. Processor output line 7-29 goes lowturning on the transistor Q1 and thus bringing the scanner rechargeinput to plus five volts. Internally the first scanner elementcapacitors are charged in the dummy and video arrays through theirrespective MOS transistors. Processor output line 7-27 sends one pulseto the scanner CLOCK input and the scanner shift register turns off thefirst element, then turns on the second element MOS transistor, and thesecond set of capacitors in the dummy and video arrays are recharged.Processor output 7-27 continues pulsing the clock input of scanner A3until all 1024 capacitor elements have been charged. In addition, theintegrating charge capacitor is charged to plus five volts.

The processor initiates the signal at 7-7 that fires the flash tube, andthe bar code pattern is reflected through optics onto the scannerphotodiode video array. Where light falls, the photodiode capacitorsdischarge.

Processor output 7-28 leading to the START input of the scanner goeshigh then low, resetting the scanner shift register to the first elementposition.

The MOS transistor is turned on and the charge from the integratingcharge capacitor discharges into the photodiode's associated capacitor.If the element was exposed to white light, i.e. a white bar, thecapacitor is discharged. The integrating charge capacitor equalizes withthe photodiode capacitor. If the element was dark, the capacitor wouldnot discharge and the integrating charge capacitor would discharge verylittle. A MOS buffer amplifier senses the capacitor charge and placesthe voltage level on scanner output line 7-40 of component A3. The dummyarray element capacitor also is charged by the integrating chargecapacitor associated with this array. A second MOS amplifier places thecapacitor voltage level on scanner output line 7-41.

Scanner output lines 7-40 and 7-41 change simultaneously in potential asa result of switching noises coupled into the arrays but only output7-40 contains valid video information. The small capacitor size limitsthe charge that can be held and it begins dissipating rapidly. Thisfactor plus various circuit losses limits the output voltage swings atoutput lines 7-40 and 7-41 between zero and four millivolts (4 mV).

Processor output lines 7-29 returns low and the transistor Q1 turns onand biases the scanner RECHARGE input to five volts so that thephotodiode's capacitor and integrating charge capacitor recharge to plusfive volts in both arrays.

Processor output 7-27 pulses high then low to the scanner CLOCK input,stepping the internal shift register to the second element in both thevideo and dummy arrays. The above sequence repeats and the secondelement capacitor is read out to the processor via output lines 7-40 and7-41.

Scanner outputs 7-40 and 7-41 contain noise impulses from variousswitching circuits. These outputs are presented to a balanceddifferential input operational amplifier A6. The operational amplifierA6 cancels the noise of equal amplitude and phase.

The video output 7-40 of scanner component A3 contains valid data notpresent on output 7-41 so that this valid data is not cancelled andinstead is amplified to a usable level for the following circuits. Theamplifier provides a voltage input to output gain of approximately 68times. Across the scanner output is a DC balancing network R6 through R9and a simple noise filter to permit the differential amplifier A6 toproduce a cleaner output.

Before the processor steps the scanner to the next element, it samplesthe differential output from amplifier A6. For this purpose output line7-30 goes high to the bilateral switch A51 enabling it to pass thesignal output from operational amplifier A6 to charge capacitor C3 of asample and hold circuit. After a preset period processor line 7-30returns low and capacitor C3 holds the output of operational amplifierA6.

A zero crossing detector is associated with the output of capacitor C3and comprises an operational amplifier A41, two diodes CR1 and CR3,resistors R12, R13 and R14 and capacitor C4. The signal from the scanneris a sine wave signal and this signal is squared by means of the zerocrossing detector. The operational amplifier gain is set at four andamplifies the incoming wave form. Capacitor C4 is also charged but at aslower rate and its voltage remains lower. When the incoming wave formrises to within 0.7 volt of the capacitor peak voltage the secondoperational amplifier A42 senses the voltage change and its output snapsto the opposite state. The diode CR2 is forward biased and dischargescapacitor C4 while the input falls. When the input begins to rise andcomes within 0.7 volt, the other diode CR3 is turned on and the secondoperational amplifier A42 senses this difference and the output changesto the opposite state.

The processor A1 samples input 7-2 (DATA IN) for a signal level. Afteropening the sample gate A51 by means of line 7-30 the program waits forseveral milliseconds to allow the operational amplifiers to stabilize.The processor A1 checks the input port 7-2 at a time when theoperational amplifier output will be a valid high or low level.

The processor shifts the scanner to look at the next element thensamples if the level is high (corresponding to a white bar area) or low(corresponding to a dark bar area). The processor keeps track of thenumber of elements that are high (white) and when the black area starts,stores the number of white elements in memory and begins counting thedark elements. When the white area begins, the dark element count isstored and the processor begins counting the white elements. After all1024 elements have been read, the processor has a pattern of white anddark element counts corresponding to the dark and white widths of thecode pattern. The processor program algorithm uses these counts toderive the bar code number.

If the final number does not match its check number or the number ofbars is incorrect, the processor repeats the read process again until acorrect number is produced. For a point of sale unit, the processor willretry for twenty times, then turns off. Releasing the switch S1 resetsthe processor for the next read cycle. For a portable unit, because itruns at a slower rate, the processor will continue flashing of the lightsource MFT until the pattern number is recognized or the unit switch S1is opened.

When a valid pattern number is derived, the processor converts thenumber to an ASCII character string and outputs these to a bidirectionalline driver A2 shown at the upper right in FIG. 7. The TTL (transistortransistor logic) level data is converted to a differential signal andis sent to a suitable receiver via output line 7-42 and 7-43.

On a portable unit, the processor output port is tied directly to theportable interface module. The portable interface module then gates thedata signal to the model 101 unit previously mentioned. The portableinterface module also converts the EIA level signals from the model 101unit to the TTL level required by the circuitry of FIG. 7.

For use with a point of sale unit, the processor will provide an outputat line 7-44 to beep the small on board speaker B1 when there is a goodscan, as well as supplying an enabling signal to output line 7-45 so asto light a green LED indicated at LED1 at the lower right of FIG. 7. Thediode LED2 emits red light so as to indicate an error condition. Theportable unit does not require a speaker and relies upon the model 101to sound its internal beeper element for a valid number.

FIG. 8 is a plot of a specific exemplary optical system embodying lenses91-95, stop aperture member 97 with aperture 98, and showing opticalsurfaces S1-S4 and S6-S11 of the lenses 91-95 in a plane through therespective vertices at axis 81.

The system of FIGS. 8-14 has essentially the characteristics previouslydescribed including a resolution at ± fifteen degree converging marginalrays 51, 52, FIG. 3, of forty line pairs per millimeter, and a depth offocus of about twenty-five millimeters, and a close-in optimum focalplane located about six millimeters in front of the front surface ofwindow 34. The system can resolve the previously described high densitybar code with five mil code intervals and a 1.8 inch length on a surfacewith a radius of curvature of about 1.25 inch. Thus the depth of fieldfor sensing sharply curved bar code patterns extend to at least tenmillimeters in front of the front surface of window 34.

In FIGS. 8-14, the focal length of the system is 24.23 millimeters andthe magnification is -0.3300. The f-number is f/8.3.

FIG. 9 is a plot showing lateral aberrations of the lens system forgreen, blue and red wavelengths of light. The ordinate shows relativepupil height, and the abscissa is plotted for image heights H' inmillimeters. In each of FIGS. 8-14, the solid lines T refer to thetangential plane while the dash lines refer to the sagittal plane. InFIG. 9, the dotted lines refer to the "SAG Y" or Y component of thesagittal ray fan.

FIGS. 10 and 11 show plots of the optical transfer function withordinate scales of relative values from zero to one for modulation, andwith abscissa values in millimeters. FIG. 10 is taken for the "ThroughFocus" condition and FIG. 11 refers to the "Best Focus" condition of-0.01 millimeter as shown in FIG. 10, the lowermost plot.

FIGS. 10 and 11 show the desired resolution of forty cycles permillimeter. Again the solid lines are for the T or tangential plane andthe dash lines are for the S or sagittal plane. The dotted lines in FIG.11 show the phase variation of the optical transfer function.

The five plots in each of FIGS. 10 and 11 are for respective objectheights H in millimeters, namely H=-36 mm, H=-30.6 mm, H=-25.1 mm,H=-12.6 mm, and H=0 mm.

FIGS. 12-14 are plots showing radial distortion, geometrical (classical)astigmatism, and MTF astigmatism. The ordinate scale shows relativevalues between zero and one, while the abscissa scale is in millimetersrelative to the focus position.

An exemplary set of specifications of the lens system which gave theresults of FIGS. 8 through 14, is as follows, (the optical surfacesbeing indicated in parenthesis for the respective lenses):

    ______________________________________                                        Exemplary Lens                                                                System Specification                                                                                           Clear                                        Lens Ref.                        Aperture                                     Number    Radius       Thickness (diameter                                    (and Lens (milli-      (milli-   milli-                                       Surface)  meters)      meters)   meters)                                      ______________________________________                                        91(S1)    13.5153      2.40000   6.98                                         91(S2)    -17.1251     1.10247   6.04                                         92(S3)    -10.8715     1.40000   4.75                                         92(S4)    -37.7869      .50000   4.03                                         97(S5)    plano         .50000   3.69                                         93(S6)    37.7869      1.40000   3.83                                         93(S7)    10.8715      4.31965   4.31                                         94(S8)    17.1251      2.40000   8.50                                         94(S9)    -13.5153     12.00000  8.91                                         95(S10)   -7.9373      2.00000   11.08                                        95(S11)   -37.4635     12.04436  13.68                                        ______________________________________                                    

Lenses 91, 94 and 95 are of an acrylic lens material known as type 493572, and lenses 92 and 93 are of a polystyrene lens material, type 592307.

In FIG. 8, the following dimensions apply as system first orderproperties:

f/9.00, H=-30.000 mm

magnification -0.4000

OBD=-91.9562 mm (object plane 0 to S1)

BRL=28.0221 mm (S1 to S11 along axis 81)

IMD=12.0444 mm (S11 to image plane I)

OVL=133.023 mm (object plane 0 to image plane I)

In FIG. 4, the axis of the elliptical reflector portion 35a mayintersect axis 64 at ten millimeters in front of the front surface ofwindow 34.

The details of a lens system which is effective to transmit an opticalimage of a bar code pattern from a sensing field 50 with a depth ofabout one inch and a width of about 2.5 inches to a flat photodetectorsurface twenty-five microns wide and about one inch in length, is asfollows:

mirror 41 at an angle of 57.5 degress to axis 81, plus or minus fifteenminutes of arc;

distance along axis 64 from bar code sensing region 50 to the frontreflective surface of mirror 41, about 46.5 millimeters;

distance along axis 80 from the front reflective surface of mirror 41 tothe front reflective surface of mirror 43, about 20.5 millimeters;

mirror 43 at an angle of 75 degress plus or minus ten minutes of arc,relative to axis 81;

distance along axis 81 from front reflective surface of mirror 43 tofirst lens surface (S1) of lens 91, about 19.5 millimeters;

distance along axis 81 from first lens surface (S1) of lens 91 to backlens surface (S9) of lens 94, about fourteen millimeters;

distance along axis 81 from the back lens surface (S9) of lens 94 to thevertex of the concave front surface (S10) of lens 95, about twelvemillimeters;

distance along axis 81 from the back convex surface (S11) of lens 95 tothe front reflective surface of mirror 103, about 7.5 millimeters plusor minus 0.1 millimeter;

distance along axis 104 from the front surfave of mirror 103 to theimage plane of photodetector 24, about 3.5 millimeters plus or minus 1millimeter;

mirror 103 at an angle of about 37.5 degrees plus or minus ten minutesof arc, relative to axis 81;

angle between axis 81 and the plane of the printed circuit board 20,about fifteen degrees.

Thus, the total optical distance along axes 64, 80, 81 and 104 is about125 millimeters. This optical path occupies a physical length of thecasing 14 of about seventy-five millimeters, so that a substantialreduction in the length of the forward portion of unit 10 is achieved.

FIGS. 15 and 16 show the circuitry for interface 17 when it isassociated with a Model 101 portable system corresponding to component16 in FIG. 1.

For the case where the circuitry of FIGS. 15 and 16 is associated withthe reader circuit of FIG. 7, switch S1 will be decoupled from processorA1, and actuation of button 18 to close switch S1 will be transmittedvia conductors 7-5, FIG. 7 to point 7-43 shown at the upper right ofFIG. 7, and from this point via conductor 8-1, FIG. 16, to the"PROXIMITY". The interface module 17 of FIGS. 15 and 16 plugs into themodel 101 unit 16 and provides any required level conversion between themodel 101 and the reader unit of FIG. 7. The interface module of FIG. 16generates plus 400 volts for the flash tube and the minus ten volts forthe scanner module A3. Both of these supplies and the plus five voltsfrom output 8-2 of FIG. 16 are switched at the interface module underModel 101 control.

A scan is initiated when the trigger switch S1, FIG. 7, is depressed.This gives a "PROXIMITY" signal to the model 101 via conductor 8-1 inthe same manner as a prior art scanning wand. After receiving PROXIMITY,the model 101 checks XOVER to verify that the high voltage is charged toan acceptable level. If not, the model 101 circuit raises RTS at 8-4,FIG. 15 to enable the high voltage charge circuit. The model 101 thenwaits for XOVER to go low, or up to 750 milliseconds, whichever comesfirst. If the XOVER signal does not indicate a valid high voltage withinthe 750 millisecond time-out, a charge error is indicated. If XOVER goesvalid within the 750 millisecond timeout then the model 101 drops RTSand raises DTR at 8-5, FIG. 15. The DTR signal is used by the interfacemodule to switch the low voltage supplies to the reader unit of FIG. 7.

After raising DTR, the model 101 waits for a Bell (07 HEX) from thereader circuit of FIG. 7. The time-out for this is also 750milliseconds. If the Bell is not received, a bad scan is assumed. Afterreceiving the Bell, the model 101 sends a three character control wordto the reader of FIG. 7. The first character is the minimum lengthexpected, added to an ASCII 0 (30 HEX), the second character is themaximum length expected, added to an ASCII 0 and third character is anASCII ACK (06 HEX). The minimum and maximum are sent in this fashion toreduce communication overhead and still maintain an ASCII protocol.

After the control word is sent, the model 101 turns on SCAN POWER at8-6, FIG. 16 to enable the strobe. The model 101 monitors XOVER todetect a flash and waits up to 100 milliseconds before assuming a badscan. After XOVER at 8-8, FIG. 16, goes low, the model 101 waits up to750 milliseconds for the reader to send the decoded bar code data. If nodata is received at line 8-10, FIG. 16, within 750 milliseconds or ifthe reader sends an ASCII "*", a bad scan is indicated and a retry willbe attempted if PROXIMITY at line 8-1 is still present.

If valid data is received from the reader, then the first characterindicates which type of label was scanned. The decoded label thenfollows with a modulus ten hash digit, and ASCII carriage return, and anASCII line feed added onto the end.

If the data meets the model 101 requirements for a good scan, then themodel 101 drops DTR at conductor 8-5 and powers off the reader unit. Ifnot, then an ASCII NAK is sent to the reader, and a retransmission isrequested. If the data was good, then the model 101, under applicationcontrol, can indicate a good scan on the reader by turning on SCAN POWERat 8-6, FIG. 16.

FIG. 15 shows the circuitry at 8-11 for the flash tube firing. When theRTS input 8-4 is active, the 300 volt direct current generator chargesits output capacitor to the maximum voltage V_(M) and is shut off by thesignal XOVER until the output voltage reaches a fixed lower voltageV_(L) at which point the 300 volt generator is started until the outputreaches V_(M). If RTS is inactive, the 300 volt generator is off.

Section 8-12 in FIG. 15, supplies minus ten volts to output 8-1, whichin turn supplies component A3, the diode array chip A3 of FIG. 7. WhenDTR at 8-5 is active, conductor 8-14, FIG. 16 is also active so as toswitch plus five volts from the model 101 to output line 8-2 via circuitblock 8-15, so that the processor A1 is powered up.

A data link circuit is indicated at 8-16 in FIG. 16 which interfaces theREAD (RD) signal and the TRANSMIT DATA (TD) signals from the model 101over a single line 8-10 to the reader processor A1 via terminal 7-42 atthe upper right in FIG. 7.

The proximity line 8-1 of FIG. 16 is an input to the model 101indicating that the operator has depressed the reader button 18requesting a read operation.

The SCAN POWER line 8-6 is an output from the model 101 allowing theflash tube to be fired by the reader processor A1 (via output 7-7).

In operation, the model 101 receives a request to scan (PROXIMITY)signal via conductor 8-1 FIG. 16 from the reader circuit of FIG. 17. Themodel 101 raises DTR at 8-14 which turns on the reader processor A1. Thereader processor sends a "Bell" signal to the model 101 via terminal7-42 and conductor 8-10, FIG. 16. The model 101 checks XOVER at 8-8 forfull charge. When 300 volts is charged (XOVER) the model 101 sends thereader a go ahead character via conductor 8-10, FIG. 16, and terminal7-42, and enables the flash via SCAN POWER at 8-6, FIG. 16. The readerdecodes the data from the scanner A3, FIG. 7, and sends a character orcharacters back to the model 101 via terminal 7-42 and conductor 8-10,FIG. 16. If a valid character is read, it is passed to the model 101.The cycle is complete and will not start again until the button 18 isreleased and depressed again by the operator. If the reader gets aninvalid code a character (*) is sent to the model 101 indicating no readand the cycle starts again.

In the portable application, the reader unit operates from the batterypack of the model 101 and to prolong its life, the central processingunit A1, FIG. 7, is powered down when not needed.

When the trigger switch S1 is closed, the model 101 proximity line, 7-5,FIG. 7, 8-1, FIG. 16, goes low. The model 101 applies five volts to thecentral processing unit A1. The capacitor charges and above 2.5 volts atC1, FIG. 7, releases the central processing unit A1 to operate. In thismode, however, conductor 7-4 and the upper plate of capacitor C1 aredisconnected from the gate of switch A54, switch A54 instead beingcontrolled via line 7-6 as shown in FIG. 16. In addition, output line7-7 from processor A1, FIG. 7, is isolated from the flash tube circuitby the bilateral switch A54. During power-up and down, conductor 7-7from the processing unit A1 changes unpredictably and could flash thelamp, so that the bilateral switch A54 is opened. Because the bilateralswitch A54 is controlled by the same signal that drives the green LED 1(good scan), FIG. 16, the switch A54 is only turned on for a short time.It is timed to coincide with the reader flash signal from conductor 7-7at the output of processor A1. The switch A54 is also turned on duringthe time the green LED 1 is on to indicate a good scan.

In the commercial equipment, fixed base, versus portable components 16were implemented by a circuit arrangement which eliminated the need forjumpers by going to a cut-only arrangement.

To correct a band width problem, the op-amp A6 was changed to a typeCA3130E. This part has a much higher gain-band width product than theamplifier previously used. It is also more stable over the temperaturerange and voltage range. The second and third stages use an LM358N, (A41and A42, FIG. 7) which was comparable to a previous part.

The recharge control transistor Q1 was changed from a 2N3906 to a VP0106to eliminate the need for two resistors. The existing circuit wasstabilized over temperature by the addition of a 2.2 kilohm resistor,but it became apparent that there was no room for the extra resistor.The VP0106 also eliminated a further resistor allowing other parts to bemoved around.

In checking the alternating current noise adjustment at R8, FIG. 7, itbecame apparent that there was an unknown noise element. This was foundto be caused by the lack of output load on amplifier A6. By adding R27,a ten thousand ohm pull-down resistor to the output of the CA3130Eoperational amplifier, the noise was eliminated. After adding R27, theadjustment of R8 was easy to complete.

The circuits as shown herein were deemed ready for release toproduction. The changes indicated were considered to accomplish somesignificant improvements.

Exemplary product specifications for a commercial reader unit inaccordance with the present invention are as follows:

Using a standard UPC-A label, the read rate design goals are:

First Read Rate: 95%

Second Read Rate: 98%

Third Read Rate: 99.5%

Not more than 7.3 errors in ten thousand accepted reads (per "The Effectof the Design of the IBM Proposed UPC Symbol and Code on ScannerDecoding Reliability").

Depth of field: Up to 0.4 inch (ten millimeters)

The reader will read bar codes with a minimum bar/space width of 7.5mils (0.0075 inch) at a contrast ratio of 50% or greater. Each bar orspace must be within plus ten percent of its nominal size, and themaximum width of a bar code is 1.8 inches from first start bar to laststop bar, including add on, if any. A quiet zone of not less than fivetimes the narrowest element of the start or stop bars is required oneach end.

Minimum label radius must be greater than 1.25 inches for a 1.8 inchlabel.

The reader will currently support the following codes: UPC-A, UPC-E,EAN-13, and EAN-8 with or without add-on 2 or 5.

The scanning modules are encoded in ROM and can be modified to supportother bar codes at the factory.

Pursuant to 37 CFR 1.96 (a)(2)(ii), a computer printout (in continuousweb form) is found in an accompanying protective cover and is designated"COMPUTER PRINTOUT APPENDIX PURSUANT TO 37 CFR 1.96(a)(2)(ii)". For thesake of identification of this material, it may be noted that theprintout sheets are numbered beginning with the third sheet as "PAGE 1"through "PAGE 57". PAGE 57 begins a "CROSS REFERENCE" listing whichcontinues for five sheets without page numbers.

The first page (without a page number) of the listing includes thefollowing notation:

"JOB=RDXIL PRINTED ON 17-DEC-81 at 03:09 PM FOR USER [1, 160]"

It will be apparent that many modifications and variations may beeffected without departing from the scope of the novel concepts andteachings of the present invention.

What we claim:
 1. In a portable bar code reader a hand-held bar code reader unit having an elongated relatively narrow hand grip portion for grasping in the hand of a user and having an enlarged reader head portion of greater width than said hand grip portion,said elongated hand grip portion having a length and cross sectional configuration so as to be grasped by the hand with all fingers in gripping relation thereto, and said enlarged reader head portion having a length less than the length of said elongated hand grip portion, said reader head portion having extended window means with a width dimension greater than the width of said hand grip portion which is to be gripped by the fingers of a hand, extended light source means in said reader head portion for producing a sheet of light energy directed outwardly from the reader head portion through said window means over substantially the entire width of said window means so as to flood a bar code sensing region in front of said window means having a width dimension approximately equal to the width of said window means, having a depth dimension equal to at least about ten millimeters and a height dimension equal to at least about one millimeter, such that a bar code pattern in the sensing region will reflect light from said extended light source means along an optical axis directed generally normal to said window means, and, lens means for focusing bar code patterns in said sensing region onto an image plane in said reader unit with a resolution of at least forty line pairs per millimeter over a depth range of at least ten millimeters such that bar code patterns with marked curvature as well as flat bar code patterns are read with high resolution and accuracy.
 2. In a portable bar code reader according to claim 1, said lens means focusing bar code patterns with said resolution of at least forty line pairs per millimeter over a depth range of at least ten millimeters in said sensing region such that bar code patterns with marked curvature are read with said resolution of at least forty line pairs per millimeter.
 3. In a portable bar code reader according to claim 1, said reader head portion having a first mirror means spaced from said window means along said optical axis for receiving reflected light from a bar code pattern in the sensing region and for re-reflecting such light along a second optical axis directed generally toward said window means, and having a second mirror means nearer to said window means than said first mirror means, said second mirror means being disposed relative to said second optical axis so as to direct light from the first mirror means along a third optical axis toward said lens means, and said lens means being located more remote from said window means than said second mirror means.
 4. In a portable bar code reader according to claim 3, said lens means having stop aperture means providing an aperture for light directed parallel to the third axis with a width dimension in a lateral direction which corresponds with the high resolution direction of a bar code pattern in the sensing region, said width dimension of said aperture being not more than about two millimeters.
 5. In a portable bar code reader according to claim 2, said lens means having stop aperture means with an aperture of a width dimension of about two millimeters in a lateral direction corresponding to the high resolution direction of the bar code pattern.
 6. In a portable bar code reader according to claim 4, the lens means causing lateral marginal rays of the light energy from the second mirror means which lie in a lateral plane corresponding to the high resolution direction of the bar code pattern to converge in the vicinity of said aperture and thereafter to diverge so as to occupy a laterally extended region at the image plane of the reader unit, said second mirror means having an operative width between the lateral marginal rays generally corresponding to the lateral extent of the image of the bar code pattern at said image plane of the reader unit.
 7. In a portable bar code reader according to claim 1, said lens means having stop aperture means with an aperture having a width dimension in a lateral direction which corresponds with the high resolution direction of a bar code pattern in the sensing region, and having a height dimension in a direction at right angles to said lateral direction, and corresponding to a direction parallel to the bar of a bar code pattern in the sensing region, the ratio of the height dimension of said aperture to said width dimension being at least about two to one. 